Cultured Drosophila melanogaster cells are responsive to the steroid hormone 20-hydroxyecdysone (ecdysterone). The transcripts of two copia-like transposable elements, 412 and 1731 were examined in cells treated for different lengths of time by the hormone. Using dot-blot and Northern-blot analysis, we have shown that the transcripts of these two retrotransposons were rapidly decreased by ecdysterone treatment.